In order to realize a photometry/ranging solid state image pick-up device having high performance AE and multi-point functions by a single chip, a plurality of ranging photoelectric conversion element columns 1A to 7A and 1B to 7B for multi-point ranging and automatic focusing of a plurality of positions in a photographing area, spot photometry photoelectric conversion elements S1 to S7 for spot photometry of a plurality of ranging positions, and a whole area photometry photoelectric conversion element WO for photometry of a whole of the photographing area are integrated on the same semiconductor substrate 107. By comparing a spot photometry value with a whole area photometry value, it becomes possible to distinguish between a front light scene and a rear light scene.
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1. A solid state image pick-up device comprising:
a plurality of ranging photoelectric conversion elements for multi-point ranging and automatic focusing of a photographing area;
first photometry photoelectric conversion elements for spot photometry of each ranging position of each of said ranging photoelectric conversion elements; and
a second photometry photoelectric conversion element for photometry of the photographing area,
wherein said ranging photoelectric conversion elements, said first photometry photoelectric conversion elements and said second photometry conversion element are integrated on a same semiconductor substrate.
15. A camera comprising:
a solid state image pick-up device comprising:
a plurality of ranging photoelectric conversion elements for multi-point ranging and automatic focusing of a photographing area,
first photometry photoelectric conversion elements for spot photometry of each ranging position of each of said ranging photoelectric conversion elements, and
a second photometry photoelectric conversion element for photometry of the photographing area, wherein said ranging photoelectric conversion elements, said first photometry photoelectric conversion elements and said second photometry conversion element are integrated on a same semiconductor substrate;
a detection region for detecting an object image;
a lens for focusing light to said detection region; and
a signal processing circuit for performing ranging and photometry controls in accordance with a signal supplied from said solid state image pick-up device.
14. An image pick-up apparatus comprising:
a solid state image pick-up device comprising:
a plurality of ranging photoelectric conversion elements for multi-point ranging and automatic focusing of a photographing area,
first photometry photoelectric conversion elements for spot photometry of each ranging position of each of said ranging photoelectric conversion elements, and
a second photometry photoelectric conversion element for photometry of the photographing area, wherein said ranging photoelectric conversion elements, said first photometry photoelectric conversion elements and said second photometry conversion element are integrated on a same semiconductor substrate;
a detection region for detecting an object image;
a lens for focusing light to said detection region; and
a signal processing circuit for performing ranging and photometry controls in accordance with a signal supplied from said solid state image pick-up device.
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3. A solid state image pick-up device according to
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8. A solid state image pick-up device according to any one of
9. A solid state image pick-up device according to
10. A solid state image pick-up device according to
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13. A solid state image pick-up device according to
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1. Field of the Invention
The present invention relates to a solid state image pick-up device having a photometry function and an automatic focusing function. More particularly, the invention relates to a photometry/ranging solid state image pick-up device to be used with a lens-shutter compact camera and to an image pick-up apparatus using such a device.
2. Description of the Related Art
A solid state image pick-up device disclosed, for example, in U.S. Pat. No. 5,302,997 is used as an automatic focusing (AF) sensor with a photometry (auto exposure: AE) function of a lens-shutter compact camera. A schematic layout of a solid image pick-up device is shown in FIG. 16. In
Two linear sensors 40 and 42 are used in order to measure a distance of an object through phase difference detection. An AF sensitivity representative of a ranging precision can be expressed by:
AF sensitivity=D×f/P
where P is a pixel pitch and f is a focal length of a range taking lens. A solid state image pick-up device having an AF sensitivity of about 5.000 is presently available. If the pixel pitch is about 10 μm and a lens focal length is several mm, the base line length D is in the range from 5 mm to 8 mm. An invalid region exists therefore between the linear sensors 40 and 42. However, since the AE sensor 30 is formed in this area, the area of the semiconductor substrate can be used efficiently. The AE and AF sensors are implemented on one chip, this contributing to compactness and low cost of a camera.
This AF sensor has only one central ranging point and does not concern about multi-point ranging. In addition, the photometry function is not satisfactory in that a proper exposure cannot be obtained for a rear light scene, and the photometry range is narrow because an output of the photometry sensor is linear.
The invention has been made in order to solve the above-described problems. An object of the invention is to provide a photometry/ranging solid state image pick-up device having a photometry function suitable for multi-point ranging.
In order to achieve the above object, an embodiment provides a photometry/ranging solid state image pick-up device comprising: a plurality of ranging photoelectric conversion elements for multi-point ranging and automatic focusing of a plurality of positions in a photographing area; first photometry photoelectric conversion elements for spot photometry of each ranging position of each of the ranging photoelectric conversion elements; and a second photometry photoelectric conversion element for photometry of the photographing area, wherein the ranging photoelectric conversion elements, the first photometry photoelectric conversion elements and the second photometry conversion element are integrated on a same semiconductor substrate.
Another embodiment of the invention provides a photometry/ranging solid state image pick-up device comprising: a plurality of ranging photoelectric conversion elements for multi-point ranging and automatic focusing of a plurality of positions in a photographing area; first photometry photoelectric conversion elements for spot photometry of each ranging position of each of the ranging photoelectric conversion elements; a second photometry photoelectric conversion element for photometry of the photographing area; means for logarithmically compressing photoelectric current output from each of the first and second photometry photoelectric conversion elements; means for controlling an accumulation time of the ranging photoelectric conversion elements; a timing generator circuit for driving the ranging photoelectric conversion elements and the first and second photometry photoelectric conversion elements; a band gap circuit for generating a reference potential; and a thermometer circuit for monitoring a temperature of a semiconductor substrate, respectively integrated on the same semiconductor substrate.
Embodiments of the invention will be described in detail with reference to the accompanying drawings.
Reference numeral 103 represents an AE sensor photodiode area including seven spot photometry photodiodes S1 to S7 and a whole area photometry photodiode WO. Reference numeral 104 represents an AE output circuit for processing an AE sensor signal. Reference numeral 105 represents an analog circuit including an AGC circuit and the like to be later described. Reference numeral 106 represents a digital circuit including a timing generator circuit, and Multiplexer and I/O circuit. Reference numeral 107 represents a Si semiconductor substrate. In this embodiment, the AF sensor blocks 100 and 101, AF sensor diode area 103, AE output circuit 104, analog circuit 105 and digital circuit 106 are all integrated on the Si substrate 107. D represents a base line length, and H and W represent vertical and horizontal lengths of the photometry area.
As described earlier, the AF sensor blocks 100 and 101 are constituted of the AF linear sensor circuits 1A to 7A and 1B to 7B.
In
The photodiode array includes pn junction photodiodes for performing photoelectric conversion. The sensor amplifier array is a differential amplifier circuit for amplifying photoelectrically converted signals output from the photodiodes. The maximum value detection circuit array is a circuit for detecting the maximum value of signals output from the differential amplifier circuit. The signal output circuit array (minimum value detection circuit array) is a circuit for detecting the minimum value of signals output from the differential amplifier circuit (or a circuit for amplifying a sensor signal and outputting it). The shift resister array (scanning circuit) is a circuit for outputting a sensor signal serially. These constituent elements shown in
In this embodiment, ranging is performed based upon phase difference detection made by pairs of the AF sensors 1A and 1B, 2A and 2B, 3A and 3B, 4A and 4B, 5A and 5B, 6A and 6B, and 7A and 7B, respectively. Horizontal linear sensors 1A to 7A shown in
The AF sensor circuit shown in
In the AF sensor circuit structured as above, the noise clamping circuit is provide at the front stage of each of the maximum and minimum value detection circuits so that it is possible to remove reset noises generated by the photodiode and FPN generated by the sensor amplifier and maximum and minimum value detection circuits. When a minimum value is to be output, the constant current source at the output stage of each voltage follower circuit of the source follower type at the final output stage of each pixel is turned off to connect the output of each voltage follower circuit to the common output line. When an image signal is to be output, the constant current source at the output stage of each voltage follower circuit is turned on to sequentially connect each voltage follower circuit to the common output line and obtain a serial image signal. With these operations, the minimum value detection circuit and signal output circuit can be combined so that the chip can be made small.
The AE sensor photodiode area 103 has the whole area photometry photodiode WO and seven spot photometry photodiodes S1 to S7. The AE output circuit 104 includes a circuit for logarithmically compressing a photoelectric current output from each photodiode. AE sensor circuits S1 to S7 and an AE sensor circuit WO in an AE output circuit 104 shown in
Vout=Vc+(kT/q)ln(Ip/Is)
where k is the Boltzmann's constant, T is an absolute temperature, q is an elementary charge, Ip is a photoelectric current, and Is is a reverse saturation current of the diode. An Is correction circuit (refer to
The analog circuit 105 is constituted of automatic gain control (AGC) circuits 1 to 7 for controlling the accumulation time of each AF sensor, a reference potential generation circuit (band gap circuit) for generating a reference potential, an intermediate potential generation circuit for generating an intermediate potential such as VRES and VGR necessary for the sensor circuits, and a signal amplification circuit for amplifying a signal and output it to an external. Each AF sensor is a charge accumulation type photoelectric conversion element. The reference potential is necessary for determining the reset and clamp potentials of the AF sensor.
The digital circuit 106 is constituted of a timing generation circuit (TG) to be used for driving the sensor, an I/O circuit for communication with an external micro computer and a multiplexer (MPX) for selecting each signal and outputting it to an external. Although the whole area photometry photodiode WO measures light in the whole area, it may measure light in a partial area of the photographing area. This applies to other embodiments to be described later.
In the embodiment, the AE and AF sensors are made of CMOS circuits so that they can be manufactured only by CMOS processes. Since various CMOS circuits (analog and digital) can be fabricated on a chip with good consistency, a variety of intelligent peripheral circuits can be fabricated on a chip. This embodiment can realize a multi-point ranging type AF sensor with a rear light detection AE function. The invention is applicable not only to CMOS sensors but also CCD, BASIS, SIT, SMD, AMI and the like.
As the seven-point ranging is reduced to the five-point ranging, the chip can further be made small. A three-point ranging such as shown in
By applying these sensors to a compact camera having a high zoom magnification and selectively using the multi-division AE areas and multi-point AF positions depending upon the zoom type, finer photometry becomes possible. This embodiment can realize a multi-point ranging type AF sensor with a rear light detection AE function.
This embodiment realizes a photometry/ranging solid state image pick-up device having AE sensors, AF sensors, TG, I/O and other various circuits which can be fabricated on a chip by CMOS processes. In this embodiment, since the thermometer circuit is built in, it is possible to realize a photometry/ranging solid state image pick-up device which can prevent the photometry and ranging performances from being degraded by high or low temperature.
Next, an image pick-up apparatus using a photometry/ranging solid state image pick-up device of one of the first to fifth embodiments will be described.
Reference numeral 205 represents a photometry/ranging solid state image pick-up device of one of the first to fifth embodiments, for example, the first embodiment shown in
Reference numeral 212 represents a recording medium control interface (I/F) section for reading data from and writing data into a removable recording medium 213 such as a semiconductor memory. Reference numeral 214 represent an external interface unit for communication with an external computer or the like.
Next, an photographing operation to be executed by the lens-shutter digital compact camera constructed as above will be described. When the barrier 201 is opened, a main power source turns on. Then, another power source for control circuits turns on and another power source for image pick-up circuits such as A/D converter 207 turns on. In order to control an exposure amount, the whole control and arithmetic operation unit 210 fully opens the diaphragm 203 and thereafter calculates an exposure amount in accordance with the data output from the signal processing unit 208 which received signals of AE sensors of the photometry/ranging solid state image pick-up device 205 via the A/D converter 207.
In accordance with the brightness determined from the photometry, the whole control and arithmetic operation unit 210 adjusts the diaphragm 203. The whole control and arithmetic operation unit 210 also calculates a distance to an object through phase difference detection by using signals output from AF sensors of the photometry/ranging solid state image pick-up device 205. Thereafter, the lens 205 is driven to check whether an in-focus state is obtained. If not, the lens 202 is again driven to perform ranging and automatic focusing.
After an in-focus state is confirmed, main exposure starts. After the main exposure, an image signal output from the solid state image pick-up element 204 is A/D converted by the A/D converter 207, supplied to the signal processing unit 208, and stored in the memory unit 211 under the control of the whole control and arithmetic operation unit 210. Under the control of the whole control and arithmetic operation unit 210, the image data stored in the memory unit 211 is recorded in the removable recording medium 213 via the recording medium control I/F section 212. The image data may be supplied directly to an external computer or the like via the external I/F unit 214.
The photometry/ranging solid state image pick-up device is applicable not only to a digital compact camera but also to a silver salt camera and the like.
As described above, according to the invention, a solid state image pick-up device having high performance AE and multi-point AE functions can be realized on a single chip by fabricating ranging photoelectric conversion element columns for multi-point ranging of a photographing area, first photometry photoelectric conversion elements for spot photometry of ranging positions, and a second photometry photoelectric conversion element for photometry of the photographing area, respectively on the same semiconductor substrate. By using the photometry/ranging solid state image pick-up device together with a lens-shutter compact camera or the like, the camera which is compact and has high performance and low cost can be realized. By comparing a spot photometry value with a whole area (or partial area) photometry value, it becomes possible to distinguish between a front light scene and a rear light scene.
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